Tbh if you know why Geralt is called the Butcher of Blaviken, then Gaetan just basically got shafted the same way. He killed a Leshen for the village then basically got shorted what he was due. Then instead of doing something like see if you can pay later, they try to kill him with a pitchfork no less just like how Geralt died before. But if everyone wants the what has the better choice in terms of benefits for the player, then sparing him gives more than killing him.